Imaging assessment of patellar instability and its treatment in children and adolescents

Abstract

Transient patellar dislocation is a common entity in children and adolescents, characterized by lateral dislocation of the patella, usually with spontaneous reduction. Many predisposing conditions have been described, including trochlear dysplasia, excessive lateral patellar tilt, patella alta and lateralization of the tibial tuberosity. Associated injuries are bone bruises of the patella and lateral femoral condyle, tears of the medial retinaculum that include the medial patellofemoral ligament (MPFL), tears of the vastus medialis obliquus muscle, injuries of articular cartilage, and intra-articular bodies. Children who are refractory to conservative management, have a large cartilage defect, or are at substantial risk for recurrent dislocations are candidates for surgical procedures to prevent future dislocations. Procedures can include MPFL repair or reconstruction, tibial tubercle repositioning and lateral retinacular release. The purpose of this review is to illustrate the imaging findings of transient patellar dislocation in the acute setting, the normal imaging appearance after surgical intervention, and post-surgical complications.

Cadaveric-Biomechanical study on medial retinaculum: Its stabilising role for the patella against lateral dislocation

“…Patellar dislocation is a common occurrence in children and adolescents, characterised by lateral dislocation of the patella, usually followed by spontaneous reduction. During patella dislocation, soft-tissue structures, such as the medial patellofemoral ligament (MPFL), medial retinaculum (MR) and vastus medialis obliquus (VMO) muscle fibres, are usually injured, frequently leading to recurrent dislocations [9].…”

Management of Injuries to the Medial Patellofemoral Ligament: A Review

“…Imaging modalities such as MRI or computed tomography (CT) are increasingly being used because of their ability to better visualize patellar tracking, MPFL lesions, bony deformities, and chondral lesions as compared with standard radiographs. [42][43][44] Aside from the Q-angle, which has grown out of favor due to high variability, more objective measurements such as the tibial tubercle-trochlear groove (TTTG) or the tibial tubercle-posterior cruciate ligament (TT-PCL) distance are more widely used. 45 The TTTG can be measured by from CT or MRI by superimposing the axial section that best displays the bottom of the trochlear groove and the patellar tendon attachment to the tibial tuberosity.…”

Imaging of the Pediatric Knee

“…Predisposing factors to patellar instability are numerous and include trochlear dysplasia, lateral patellar tilt, patella alta, lateralization of the tibial tubercle, genu valgum, pes planus, femoral anteversion, laxity of the medial patellofemoral ligamentous complex, and excess tightness of the lateral retinaculum. 10 Radiographically, lateral patellar displacement can be seen on anteroposterior (AP) and Merchant views, a joint effusion on the lateral view, possibly with a fat-fluid level indicating the presence of an osteochondral fracture, and fracture fragments arising from the medial patella or lateral femoral condyle, indicating medial patellofemoral ligament (MPFL) avulsion injury and osteochondral impaction fractures, respectively. Radiographs can underestimate the degree of osteochondral injury and do not detect soft tissue or ligamentous injury; therefore, MRI is increasingly used to evaluate both acute and chronic patellar dislocation.…”